Combining high grain number and weight through a DH-population to improve grain yield potential of wheat in high-yielding environments

Previous yield gains in wheat have been achieved through increased expression of grain number per unit area, while fruiting efficiency has also been shown to explain improved grain number. However, combining a high grain number and weight in the same genotype is a difficult task in practical breeding. This study evaluated the progeny of a cross between two elite parents that contrast in grain number and grain weight, as a way to better understand how the two desired traits might be combined to achieve a significant boost in yield. The two parents are both high biomass elite spring wheat lines that achieve high yield through contrasting strategies: Bacanora achieves high grain number with a high density of relatively small spikes. Weebil has a lower density of larger spikes in which larger grain size is expressed. The specific objectives of this research were: (i) to evaluate grain yield performance of DH lines and parents over two seasons, (ii) to identify promising physiological traits explaining high yield performance and (iii) to determine whether these traits are also expressed at the low plant densities. Two experiments were carried out under field conditions in southern Chile where the highest yield potential of wheat has ever been recorded. In Exp. 1 the performance of the 105 spring wheat DH lines, their parents and a Chilean spring cultivar (Pandora-INIA) with similar phenology were assessed together. Results showed that it is possible to increase yield potential by combining high grain number and grain weight, thereby reducing the trade-off between both components. 42 and 50% of the DH lines showed transgressive segregation in S1 and S2, respectively. 3 and 4% of the DH lines yielded between 15,000 and 16,000 kg ha−1. Grain yield was highly correlated with above-ground biomass (R2 = 0.78, p